The present invention relates to prepared foods, such as fried snack foods, fortified with non-esterified phytosterols delivered in fats or oils that are essentially free of emulsifiers and the like, and to the utility of such phytosterols for stabilizing heated fats and oils against oxidation, as well as to the surprising bioavailability of triglyceride-recrystallized phytosterols in such foods, for decreasing plasma cholesterol levels in mammals.
It has been a widely held belief that to obtain appreciable benefit from phytosterols, i.e., either plant sterols, stanols, or combinations thereof [including beta-sitosterol, beta-sitostanol, campesterol, campestanol, stigmasterol, stigmastanol, brassicasterol, brassicastanol, clionasterol and clionastanol (collectively termed phytosterol or phytosterols)] for lowering plasma cholesterol, the phytosterol should be dissolved in an edible oil or other solvent so that it can enter micelles in the small intestine to inhibit the absorption of cholesterol.
This belief has been supported by early research carried out in the 1950s through the 1970s showing that large doses of phytosterols in their solid form, i.e., coarse powders, were required to achieve meaningful decreases in plasma cholesterol levels. For example, in 1956, Faquhar et al., (Circulation, 14, 77-82, 1956) showed that doses of 12-18 g per day of beta sitosterol (provided in divided doses) were required to achieve a 15-20% lowering of serum cholesterol in males with atherosclerosis. In another study, 9 g per day (3 g t.i.d.) of soybean-derived phytosterols were required to lower plasma cholesterol approximately 9% (Kucchodkar et al., Atherosclerosis, 23, 239-248, 1976). In yet another study, 3-9 g per day of tall oil-derived phytosterols were required to lower plasma cholesterol approximately 12% (Lees et al., Atherosclerosis, 28: 325-333, 1977). In a recent study, 1.7 g per day of finely powdered tall oil-derived phytosterols were sufficient to lower total plasma cholesterol by 9% and LDL-cholesterol by about 15% (Jones et al., Am J Clin Nutr, 69: 1144-1150, 1999).
It has been generally appreciated that phytosterols such as alpha and beta sitosterol, stigmasterol, campesterol, and the corresponding saturated (chemically reduced or hydrogenated) “stanol” species, are insoluble in water, and only slightly soluble in edible oils. Accordingly, to promote the solubilization of phytosterols, and their efficacy in lowering plasma cholesterol, U.S. Pat. No. 6,025,348 by Goto et al. describes the incorporation of at least 15% and as much as 70% by weight or more of a polyhydric alcohol/fatty acid ester (including glycerol fatty acid esters containing at least two esterified and at least one unesterified hydroxyl group such as diacylglycerols or diglycerides), into a fat. Between 1.2% and 4.7% by weight of phytosterol is incorporated into the polyhydric alcohol/fatty acid ester containing fat composition.
U.S. Pat. No. 6.139,897 by Goto et al. describes an oil or fat composition containing 80% or more diacylglycerol and up to 20% phytosterol. The high proportion of diacylglycerol assures solubility or dispersal of the phytosterol to provide a cholesterol-lowering fat substitute.
U.S. Pat. No. 5998,396 by Nakano et al., describes an edible oil containing a phytosterol, vitamin E, and an emulsifier rendering the phytosterol soluble in both the vitamin E and the edible oil.
U.S. Pat. No. 5,419,925 by Seiden et al. describes a reduced calorie fat composition based upon a substantially non-digestible polyol fatty acid polyester plus reduced calorie medium chain triglycerides and other reduced calorie fats or noncaloric fat replacements including plant sterol esters that are soluble in such fat compositions. Free fatty acids, vitamin E and tocotrienol have each been utilized by other inventors to promote the solubilization of phytosterols in fats and oils, with the expectation that the cholesterol lowering properties of various phytosterols would be improved.
U.S. Pat. No. 5,244,887 by Straub describes the preparation of a cholesterol-lowering food additive composition with plant stanols, including: (i) an edible carrier such as an oil, monoglyceride, diglyceride, triglyceride, tocopherol, alcohol or polyol, (ii) an antioxidant and (iii) a dispersant or detergent-like material such as lecithin, or other phospholipids, sodium lauryl sulfate, a fatty acid, salts of fatty acids, or a fatty acid ester. Straub cites research showing that 1.5 grams per day of a stanol mixture derived from soybean sterols lowered blood cholesterol by 15% after 4 weeks of therapy, and believes that these stanols are preferred to sterols based upon less stanol absorption from the G.I. tract and better heat stability in air than sterols.
U.S. Pat. No. 5,932,562 by Ostlund, Jr. describes an aqueous micellar mixture of plant sterol and lecithin (in a 1:1 to 1:10 mole ratio) which has been dried to a water soluble powder and which is useful as a food additive for reducing cholesterol absorption.
U.S. Pat. No. 4,195,084 by Ong describes a taste-stabilized pharmaceutical suspension of sitosterols to reduce hypercholesterolemia, in which the suspension includes the plant sterol, a chelator such as calcium disodium EDTA, a surfactant and other ingredients to assure suspension and dispersal of the phytosterol.
U.S. Pat. No. 3,881,005 by Thakkar et al. describes a pharmaceutical dispersible powder for oral administration in which sitosterols are combined with any one of a variety of excipients, and any one of a variety of pharmaceutically acceptable surfactants.
U.S. Pat. No. 6,267,963 by Akashe et al. describes a plant sterol/emulsifier complex that has a lower melting temperature than the plant sterol alone. The complex, e.g., a co-crystallized monoglyceride and plant sterol mixture, is said to facilitate incorporation of the sterol into food products without adversely affecting the texture of the food products.
As indicated above, it has been widely believed that increasing the solubility of phytosterols in fat increases their bioavailability and reduces the dose required to achieve a specified degree of cholesterol reduction. Thus, U.S. Pat. No. 5,502,045 by Miettinen et al., describes the preparation and use of the plant stanol, beta sitostanol, in the form of a fatty acid ester which is readily soluble in an edible oil, to reduce the serum cholesterol level in humans. This technology has been utilized in manufacturing the margarine product marketed under the tradename Benecol®.
U.S. Pat. Nos. 6,031,118 and 6,106,886 by van Amerongen et al. describe similar stanol fatty acid esters but provide different and reportedly improved chemical methods for their preparation. Plant sterols(from soybean oil) have also been interesterified with fatty acid esters to produce the margarine marketed under the tradename Take Control®. Clinical studies suggest that with mildly hypercholesterolemic individuals, dietary intake of between 1.5 and 3 grams per day of the free phytosterol (provided in a fatty acid esterified form) is required to decrease plasma cholesterol approximately 15%.
U.S. Pat. No. 5,932,562 by Ostlund, Jr. points out that cholesterol is absorbed from an intestinal micellar phase containing bile salts and phospholipids which is in equilibrium with an oil phase inside the intestine. Prior to recent experiments, delivery of phytosterol as a solid powder or aqueous suspension was thought to not be preferred because of the limited rate and extent of solubility in intestinal liquid phases. In fact, at least two earlier human studies showed that as much as 9-18 grams of sitosterol per day were required to decrease the plasma cholesterol level by approximately 15% when the sitosterol was provided in a coarse powdered (rather than soluble) form. Yet, esterification of phytosterols, coupled with the use of edible oils to deliver these sterols is not always practical, e,g., in formulating fat-free foods. It is in this context that Ostlund, Jr. provides a water-dispersible mixture of plant sterol and lecithin.
Using a finely milled powdered form of free phytosterols (from tall oil) suspended in a margarine (not fully dissolved or recrystallized in fat), Jones et al. have described cholesterol reduction in hypercholesterolemic humans (Jones et al., Am J Clin Nutr 69:1144-1150, 1999) and other mammals (Ntanios et al., Atherosclerosis, 138:101-110, 1998; Ntanios et al., Biochim Biophys Acta, 1390:237-244, 1998). In these studies, the efficacy based on cholesterol reduction appears to be equal to that of phytosterol and stanol esters reported by others.
Still another method of producing a fine suspension of microparticulate phytosterols in fat and water has been described by Yliruusi et al. in PCT International Publication Number WO 99/43218. The method involves first heating and dissolving beta-sitosterol in a fat or oil, and then precipitating the phytosterol with water to form a homogenous microcrystalline suspension. While this process appears more cost-effective than grinding, emulsification of fat with water causes any fat to become susceptible to oxidation and necessitates refrigeration.
The production of microparticulate phytosterols described in the prior art involves increased cost and inconvenience, e.g., the use of grinding, and can result in a mixed emulsified product that is more susceptible to oxidation and rancidity, particularly when an aqueous fat-phytosterol emulsion is involved. In fact, there are limitations and disadvantages inherent in most of the above prior methods of phytosterol preparation and delivery. These methods have included grinding, formation of fat and water mixed phytosterol emulsions, chemical modification of phytosterols, e.g., esterification, and mixing of phytosterols with substantial amounts of specialized solubilizing and dispersing agents.
A recent review article entitled “Therapeutic potential of plant sterols and stanols” (Plat et al., Current Opinion in Lipidology, 11:571-576, 2000) has summarized the results of a number of independent clinical studies in which human plasma cholesterol levels were monitored before and after ingestion of food products enriched with plant sterols and sterol esters (approximately 2-2.5 g per day). The authors conclude that LDL cholesterol levels decreased significantly, i.e., an average of 10-14%.
The description above is provided to assist the understanding of the reader, and does not constitute an admission that the cited references are prior art to the present invention.